A conventional method for manufacturing a seat having a different hardness and comprising a surface material and a foamed body integrated in one with the surface material is shown in FIG. 8 (this manufacturing method is disclosed in Japanese Patent Application No. Heisei 7(1995)-339895). This manufacturing method is carried out as follows.
Firstly, a liquid foamable mixture 82 such as a polyurethane foam and the like is injected and laminated on a first foamed body 81 as a base of a foamed body. A surface material 80 comprises a central surface portion 80' and side surface portions 80", 80'" stitched on both sides thereof. The surface material 80 is then disposed so that the central surface portion 80' is positioned on the laminated mixture 82 and the side surface portions 80", 80'" are positioned on both sides of the first foamed body 81, respectively.
Then, a pressure applying mold 84, which has a molding surface 83 having a shape corresponding to a shape of a central portion of the seat, is lowered; and the liquid foamable mixture 82 is pressed and compressed together with the surface material 80 by the pressure applying mold 84 and the first foamed body 81 when the liquid foamable mixture 82 is reacting i.e. when the mixture has completed a gas reaction thereof but is still in a visco-elastic flowing condition.
When the mixture is pressed and compressed in such a viscoelastic flowing condition, the mixture is easily deformed while the surface material is pushed back by an reactive force against the pressure applied to the mixture, and as a result, the mixture is molded together with the surface material into a shape corresponding to the molding surface of the pressure applying mold. Then, when the mixture is transformed into a solid condition, the second foamed body is formed, and when this, a back surface of the surface material 80 is integrated with the upper side of the second foamed body and the first foamed body 81 is integrated with the lower side of the second foamed body. It should be noted that a seat covered with a surface material and having a multilayer having a variety of hardness can be manufactured by changing the degree of hardness of the first foamed body and that of the second foamed body, respectively, i.e. by changing the compressibility and the like when compressing and molding the second foamed body.
As aforementioned, according to this conventional method, the first foamed body can be integrated with the second foamed body without use of a lower mold and a seat having the surface material fixed in one with the second foamed body and having a shape corresponding to the molding surface of the pressure applying mold can be manufactured.
As aforementioned, the surface material is pushed on the molding surface of the pressure applying mold by the reactive force when the foamable mixture is pressed. However, when a deep channel is provided in the molding surface of the pressure applying mold or when the molding surface of the pressure applying mold has a three dimensional complicated geometry, the reactive force of the foamable mixture is too small to form the surface material along such a complicated geometry of the molding surface of the pressure applying mold and the foamable mixture is crushed. As the result, a shape of the surface material is faded as shown in FIGS. 9A and 9B, i.e. a seat precisely following the molding surface of the pressure applying mold can not be manufactured.
In such a case, in the conventional technique, as shown in FIGS. 10A and 10B, suction slots (or slits) 101 are entirely provided in the pressure applying mold 100, and a pressure difference is provided between an inside of the surface material 102 and an outside thereof by decompressing an inside of the pressure applying mold so that the surface material can follow the surface shape of the pressure applying mold. However, a large pressure difference is required to follow the surface material along the surface shape of the pressure applying mold. The pressure difference is determined by the air permeability (i.e. a rate of air passing through or communicating in the surface material). However, in a textile typically used, it is difficult to reduce the air permeability which can achieve such a pressure difference produced by sucking such that the textile can be formed along the molding surface having a three dimensional complicated geometry. Thus, when such a typically used surface material is used, a seat having a three dimensional complicated geometry and a deep channel can not be manufactured by this pressure applying mold having the suction slots.
In use of the surface material having such an air permeability, a thermoplastic film 1021" is laminated on a back surface thereof to prevent air penetration of the surface material and is sucked to shape the surface material, as shown in FIGS. 10A and 10B. Then, the plastic film 102" is heated and softened by a heater 103 to deform the plastic film 102" permanently, and the surface material is held so that the surface material 102' can be deformed into a shape corresponding to a shape of the molding surface of the pressure applying mold. In use of such a material for preventing air penetration, not only a cost of a raw material but also the number of manufacturing steps is increased, and as a result, the whole cost is increased and the productivity is worse.
The present invention is to solve the aforementioned problem and an object thereof is to provide a seat having a surface shape corresponding to a molding surface of a mold in which a surface material thereof is integrally formed with a foamed body and to provide a method for manufacturing such a seat.
Another object of the present invention is to provide a seat in which a surface material having air permeability can be used and to provide a method for manufacturing such a seat.
Still another object of a present invention is to provide the seat in which it is not necessary to laminate a film, which is for preventing air penetration, on a back surface of the surface material and to provide a method for manufacturing such a seat.
Yet another object of a present invention is to provide the seat in which the degree of hardness of an upper layer which contacts with a person is soft and that of a lower layer which supports a weight of the person is hard and to provide a method for manufacturing such a seat.
Yet still another object of a present invention is to provide the seat in which the degree of hardness of the upper layer is partially different and to provide a method for manufacturing such a seat.